Use of Calotropis procera cysteine peptidases (CpCPs) immobilized on glyoxyl-agarose for cheesemaking.

Calotropis procera cysteine peptidases (CpCPs) have presented several potential biotechnological applications. Here, these enzymes were immobilized on glyoxyl-agarose (glyoxyl-CpCPs) with yields of 90-95 % and the recovered activities ranged from 10 % to 15 %, according to enzyme loadings (5, 10, 20, 40, and 50 mgBSAeq/g). Spectrophotometric assays and SDS-PAGE showed that the casein hydrolysis by glyoxyl-CpCPs was similar to soluble CpCPs. In addition, glyoxyl-CpCPs exhibited similar ratio of milk-clotting activity to proteolytic activity in comparison with soluble CpCPs and chymosin. Even after being stored for six months at 8 °C, the residual proteolytic activity of glyoxyl-CpCPs remained close to 100 %. Atomic force microscopy and dynamic light scattering techniques showed that the process of casein micelle aggregation after treatment with glyoxyl-CpCPs was very similar to its soluble form and chymosin. Glyoxyl-CpCPs performed well after five reaction cycles, producing cheeses with yield, moisture, protein, and fat similar to those produced with chymosin.

Ser2 from Serratia liquefaciens L53: A new heat stable protease able to destabilize UHT milk during its storage.

The heat-stable protease Ser2 is secreted by the species Serratia liquefaciens, a psychrotrophic bacteria frequently found in raw milk. To understand the physicochemical modifications of casein micelles induced by Ser2 and to confirm its implication in UHT milk destabilization, the enzyme was purified and added to microfiltered raw milk before UHT treatment. UHT milk destabilization was investigated during 90days of storage. A visual destabilization appeared after 8days of storage with the presence of sediment. Zeta potential increase and formation of aggregates were observed during the storage. Using tandem mass spectrometry, numerous released peptides from the four caseins were identified at the end of storage. Caseins were hydrolyzed in the preferential order ß->αs1->κ->αs2. No specific peptidic hydrolysed bond was detected. The present study confirmed that the presence of the protease Ser2 in raw milk can be one of the main causes of UHT milk destabilization.

Leite instável não ácido e fatores que afetam a estabilidade do leite / Not acid unstable milk and factors affecting the stability of milk

Estabilidade do leite refere-se à resistência relativa do leite em suportar o tratamento térmico industrial sem sofrer coagulação. A estabilidade do leite ao teste do álcool em princípio, é utilizada para identificar amostras de leite com alta contaminação bacteriana, devido às más condições de higiene e de conservação durante a produção primária, o que causa menor estabilidade durante o tratamento térmico. No entanto, pode ocorrer precipitação da proteína no teste do álcool, sem, haver acidez acima de 0,18g/ácido lático/100mL de leite, denominado de leite instável não ácido, que é um problema que acomete rebanhos leiteiros e/ou indústrias lácteas, que se caracteriza pela perda de estabilidade da proteína, o que resulta em precipitação na prova do álcool 72% sem, haver acidez acima de 0,18g/ácido lático/100mL de leite, gerando prejuízos a todos os elos da cadeia, já que o leite mesmo apto ao beneficiamento, sem acidez elevada é rejeitado ou subvalorizado pela indústria. No Brasil, a incidência do leite instável não ácido ainda carece de diagnóstico devido à falta de trabalhos de pesquisa, por ser um problema multifatorial, pois a estabilidade térmica do leite é um dos fatores importantes para aumentar a vida-de-prateleira de derivados lácteos, garantir adequadas condições de processamento e proporcionar maior qualidade ao consumidor final.

Stability of milk refers to the milk relative resistance to withstand the heat treatment without undergoing industrial coagulation. The stability of milk to test the alcohol in principle, is used to identify milk samples with high bacterial contamination due to poor hygiene and conservation during primary production, which causes less stability during heat treatment. However, precipitation of the protein in the test for alcohol, can occur without, having acidity above 0.18g/lactic acid/100 ml of milk, milk does not called unstable acid which is a problem affecting dairy herds and / or dairy industries which is characterized by the loss of protein stability, resulting in the precipitation test of 72% ethanol, no significant acidity above 0.18g/lactic acid/100 ml of milk, thus impairing all chain links, as the same room for processing milk without high acidity is rejected or undervalued by the industry. In Brazil, the incidence of not acid unstable milk still lacks diagnosis due to lack of research, to be a multifactorial problem, since the thermal stability of milk is one of the important factors to increase the shelf-life of dairy derivatives, ensure adequate processing conditions and provide higher quality to the final consumer.

Leite instável não ácido e fatores que afetam a estabilidade do leite / Not acid unstable milk and factors affecting the stability of milk

Estabilidade do leite refere-se à resistência relativa do leite em suportar o tratamento térmico industrial sem sofrer coagulação. A estabilidade do leite ao teste do álcool em princípio, é utilizada para identificar amostras de leite com alta contaminação bacteriana, devido às más condições de higiene e de conservação durante a produção primária, o que causa menor estabilidade durante o tratamento térmico. No entanto, pode ocorrer precipitação da proteína no teste do álcool, sem, haver acidez acima de 0,18g/ácido lático/100mL de leite, denominado de leite instável não ácido, que é um problema que acomete rebanhos leiteiros e/ou indústrias lácteas, que se caracteriza pela perda de estabilidade da proteína, o que resulta em precipitação na prova do álcool 72% sem, haver acidez acima de 0,18g/ácido lático/100mL de leite, gerando prejuízos a todos os elos da cadeia, já que o leite mesmo apto ao beneficiamento, sem acidez elevada é rejeitado ou subvalorizado pela indústria. No Brasil, a incidência do leite instável não ácido ainda carece de diagnóstico devido à falta de trabalhos de pesquisa, por ser um problema multifatorial, pois a estabilidade térmica do leite é um dos fatores importantes para aumentar a vida-de-prateleira de derivados lácteos, garantir adequadas condições de processamento e proporcionar maior qualidade ao consumidor final.(AU)

Stability of milk refers to the milk relative resistance to withstand the heat treatment without undergoing industrial coagulation. The stability of milk to test the alcohol in principle, is used to identify milk samples with high bacterial contamination due to poor hygiene and conservation during primary production, which causes less stability during heat treatment. However, precipitation of the protein in the test for alcohol, can occur without, having acidity above 0.18g/lactic acid/100 ml of milk, milk does not called unstable acid which is a problem affecting dairy herds and / or dairy industries which is characterized by the loss of protein stability, resulting in the precipitation test of 72% ethanol, no significant acidity above 0.18g/lactic acid/100 ml of milk, thus impairing all chain links, as the same room for processing milk without high acidity is rejected or undervalued by the industry. In Brazil, the incidence of not acid unstable milk still lacks diagnosis due to lack of research, to be a multifactorial problem, since the thermal stability of milk is one of the important factors to increase the shelf-life of dairy derivatives, ensure adequate processing conditions and provide higher quality to the final consumer. (AU)